TUCSON, Ariz. — NASA's Phoenix Mars Lander has flexed its robotic arm for the first time and taken a fish-eye panorama of its surroundings, mission scientists said Thursday.

"We have now achieved a major milestone for this mission," Phoenix project manager Barry Goldstein of NASA's Jet Propulsion Laboratory said via a video link in a mission briefing held here at the University of Arizona.

"I'm ecstatic to let you know that [the robotic arm deployment] was successful," said Matt Robinson, the robotic arm flight software lead at JPL. "It is raring to go. It's busted loose now and we're ready to go."

Phoenix also sent back a completed black-and-white panorama mosaic of its landing site, showing the deployed solar arrays, robotic arm, meteorological mast and the flat terrain stretching out toward the horizon. The $422 million spacecraft is designed to dig down into the Martian arctic soils to the layers of water ice thought to lie beneath the surface.

"We have a very hummocky terrain," Phoenix principal investigator Peter Smith of the University of Arizona said, describing the polygonal-shaped bumps that cover the arctic landscape and are separated by trenches in the soil. The shapes are believed to be formed by the expansion and contraction of the water ice underneath.

The images also show a scattering of "flat, tablelike rocks," as Smith described them.

The Phoenix science team has begun naming the rocks they find to keep track of them, using a fairy tale and folklore theme (so that the science team can have a little fun, Smith said). The rocks that have been named so far include Humpty Dumpty, the King's Men and Alice (in reference to Lewis Carroll's "Alice in Wonderland").

The science team plans to use the robotic arm to move some of the rocks, which are only a few inches across, to see what's underneath them. They will also investigate the origin of the rocks.

"The rocks don't come with labels, it's a little hard to tell where they came from," Smith said.

But first, mission controllers plan to test out the robotic arm's joints in higher and lower temperatures on the Red Planet, "and that's because the robotic arm is going to be required to move at a range of temperatures," Robinson explained. Weather reports from the surface so far show a high temperature at the landing site of -22 degrees Fahrenheit (-30 degrees Celsius) to a low of -112 F (-80 C).

Controllers will also position the arm so that the camera attached to its scoop can snap a picture of the surface under the lander, to make sure no rocks are there.

Scientists have divided the terrain into two parts: a "national park" area that mission scientists will leave untouched until they have better characterized the environment, and an area they can use to test out the robotic arm's digging capabilities.

"It's more of a Superfund site over there, so we're allowed to mess that part up a bit," Smith said.

Digging likely won't start until the middle of next week, mission scientists said.